不锈钢的损伤及其防止措施（7）——以事例为中心

奥氏体不锈钢的晶间腐蚀除了特别的场合外，是一种起因于晶粒间界碳化物析出的现象，因此晶间腐蚀损伤几乎都是与热处理、焊接等热的影响有关而引起的例子。晶间腐蚀是有选择性的，所以根据其进行的程度、晶粒缺落，即使叩敲也不能发出金属的声音；另外，乍一看发现不了什么异状，但是，当弯曲了看时会发现有裂纹，所以有时就形成晶间腐蚀。     

奥氏体不锈钢晶间腐蚀的控制

正在不锈钢发生的各种腐蚀中,晶间腐蚀约占10%,它会使晶粒间的结合力有所下降,在应力的作用下,极易产生裂纹,甚至碎成粉末,并且很隐蔽,从其外形上看不出来。同时它也是诱导其它腐蚀的主要原因。奥氏体不锈钢的晶间腐蚀主要是由于晶界区贫Cr所引起的,而C容易和Cr形成化合物,使Cr含量减少。为此,晶间腐蚀的防止措施是:化学成分及组织     

4Cr13环模断裂原因分析

为查找环模在使用过程中发生早期开裂的原因,对其化学成分、显微组织及断口特征进行了分析.提出了环模组织不良及环模在工作介质、环境条件形成的晶间腐蚀裂纹是造成环模断裂主要原因.     

304L不锈钢的应力腐蚀

本文研究了３０４Ｌ不锈钢氧氯化反应器上封头的应力腐蚀行为，研究结果表明，材料裂纹的产生是由腐蚀引起。在氯离子作用下首先在硅钙类氧化物夹杂物处发生点蚀，成为裂纹源，然后在应力，氯离子和硫离子三种因素作用下产生裂纹，氯离子和硫离子在裂纹处不断积聚，在应力作用下裂纹扩展，最后导致材料失效。     

电站锅炉用TP347H钢管爆裂分析

利用金相显微镜和扫描电镜等分析技术,分析电站锅炉用TP347H钢管的爆裂原因.结果表明,钢管中碳化物在高温下沿晶界聚集分布,会降低抗晶间腐蚀能力,材料的蠕变抗力下降,并在钢管表面产生沿晶裂纹,在高温高压作用下裂纹不断扩展并最终产生爆管.     

换热器用不锈钢管焊后管口裂纹失效分析

对样件进行宏观和微观形貌分析,测试样件化学成分、非金属夹杂物、晶粒度、拉伸性能、晶间腐蚀、硬度等性能指标,并通过SEM+EDS等分析手段对换热器的不锈钢管与管板焊缝处内壁裂纹进行分析和讨论。得出结论:引起裂纹最主要原因是Cu在焊接温度偏高情况下沿晶富集,致使晶界强度急剧降低,焊缝处母管内壁发生沿晶裂纹;针对该类失效给出了相应的预防和控制措施。     

椭圆形封头的受力分析

通过对椭圆形封头的受力状况和结构特性进行分析，以及与其它形式的封头进行比较，说明椭圆形封头在压力容器设计中被广泛采用的原因，指出在实际运用中应注意的问题。     

316L不锈钢饱和器焊接性探讨

焦化厂的硫酸铵饱和器,常常由于检修焊接不当加之强腐蚀工艺介质剧烈腐蚀之下,造成焊接接头的腐蚀破坏,形成晶间腐蚀、裂纹、穿孔等焊接接头缺陷和危害。因而,本文从316L不锈钢的焊接性入手,分析其晶间腐蚀,焊接热裂纹,应力腐蚀开裂,接头的σ相脆化等该材质的焊接特点,并详述了其防止的具体措施。结合实际有针对性的阐述了其该母材的焊接工艺及要点,有效的降低316L不锈钢的晶间腐蚀及其他焊接缺陷,提高了其焊接性。     

HP295钢中夹杂物对钢瓶拉延性能的影响

通过对HP295焊瓶钢制作的钢瓶封头缺陷进行分析，找到了影响钢瓶封头拉延性能的原因。结果表明，拉延焊瓶封头出现开裂是由于钢中集中分布的稀土夹杂物所致。皱折缺陷与钢中存在带状组织、钢板厚度不均以及拉延工艺有关。     

HP 295加工月牙开裂原因分析及对策

结合生产实践及加工特点,针对焊瓶钢HP295封头拉伸过程中月牙开裂缺陷产生原因进行了细致分析。分析认为:铸坯中间裂纹、长条状MnS夹杂是造成焊瓶钢加工月牙开裂缺陷的根本原因,而成分偏析、合理的组织构成和规范的加工工序亦非常重要。     

Effects of zinc coatings on the stress corrosion cracking and hydrogen embrittlement of low-alloy steel

The effects of electroplated and hot-dip zinc coatings on the fracture of low-alloy steel AISI 4140 bars tempered to hardnesses in the range Rc 33 to 49 were studied. Either electroplated or hot-dip zinc coatings decrease resistance to stress corrosion cracking,i.e., they reduceK _sc, the threshold stress intensity for stress corrosion cracking in 3.5 wt pct NaCl solution. AboveK _scelectroplated-zinc coatings do not appear to affect the crack-growth rate, although the incubation period prior to the onset of crack growth is reduced. Hot-dip zinc coatings increase stress corrosion crack growth rates slightly because of the additive effect of internal dissolved hydrogen. Hot-dip zinc coatings reduce the critical stress intensity for fracture in the absence of a corrosive environment because of embrittlement by internal hydrogen which is released from traps during hot-dip coating and confined by the inter metallic coatings which form on the steel surface in the hot dip bath. A simple fracture mechanics analysis indicates that either increasing diameter or the presence of a zinc coating lowers the critical hardness at which the stress corrosion cracking of structural bolts can occur.     

Effects of zinc coatings on the stress corrosion cracking and hydrogen embrittlement of low-alloy steel

The effects of electroplated and hot-dip zinc coatings on the fracture of low-alloy steel AISI 4140 bars tempered to hardnesses in the range Rc 33 to 49 were studied. Either electroplated or hot-dip zinc coatings decrease resistance to stress corrosion cracking,i.e., they reduceK _sc, the threshold stress intensity for stress corrosion cracking in 3.5 wt pct NaCl solution. AboveK _scelectroplated-zinc coatings do not appear to affect the crack-growth rate, although the incubation period prior to the onset of crack growth is reduced. Hot-dip zinc coatings increase stress corrosion crack growth rates slightly because of the additive effect of internal dissolved hydrogen. Hot-dip zinc coatings reduce the critical stress intensity for fracture in the absence of a corrosive environment because of embrittlement by internal hydrogen which is released from traps during hot-dip coating and confined by the inter metallic coatings which form on the steel surface in the hot dip bath. A simple fracture mechanics analysis indicates that either increasing diameter or the presence of a zinc coating lowers the critical hardness at which the stress corrosion cracking of structural bolts can occur.     

中厚板裂纹影响因素分析及预防途径探讨

裂纹是中厚板废品和不良品的主要构成部分，是降低质量指标和经济效益、影响用户使用性能的质量缺陷。通过现场试验和数理统计，对中厚板裂纹影响因素进行了定量分析和深入探讨，改善冶金工艺、优化再加热工艺和轧制规范，可以在较大程度上减缓裂纹的不良影响。     

Research status of corrosion environment failure and safety assessment of pipeline welded joint

Pipeline transportation is an economical,safe,and efficient transportation method for transporting oil,natural gas,mineral slurry,and other fluids.Welding is the most critical construction process in pipeline engineering and is crucial in the safe operation and service of an entire pipeline system.Theoretically,the girth welded joint is the weakest link in a pipeline system.The unevenness of the structure and performance of the joint caused by welding frequently results in the failure of the welded joint before the failure of the base material of the pipe body,causing the pipeline to leak or even break.For steel pipes used in an acidic corrosive medium environment,the integration of the corrosive medium and mechanical load will accelerate the failure of the welded joint.This article reviews the failure modes of pipeline welded joints in acidic corrosive media,including stress corrosion cracking,hydrogen-induced cracking,and corrosion fracture,and corrosion fatigue considering the diffusion and accumulation of H+at the crack tip.It also reviews service pipelines in acidic corrosive media.The general processing technology of pipe joint engineering critical assessment(ECA)is investigated to provide a reference for the future development of technology in this field.     

Ti－6A1－4V合金的腐蚀与磨蚀行为的研究

本文采用多种试验方法，研究了Ｔｉ与Ｔｉ－６Ａ１－４Ｖ的腐蚀与磨蚀行为。试验结果表明，Ｔｉ－６Ａ１－４Ｖ合金具有优良的均匀腐蚀、点蚀、晶间腐蚀与磨蚀性能。     

循环氨水管道泄漏原因分析及防漏措施

环氨水中含有H2S等多种腐蚀性介质,对普通的循环氨水管道有一定的腐蚀作用,循环氨水管道在制作和安装过程产生的各种残余应力和介质腐蚀的联合作用诱发了管道的应力开裂,H2S等应力腐蚀和氢损伤是造成氨水管道的泄漏主要原因。焊接时的焊接缺陷或应力腐蚀而在管道内壁形成的微小裂纹,诱发氨水管道的缝隙腐蚀。因此管道的焊接质量和焊接后的消除应力处理显得尤为重要。     

退火对钢—钢爆炸复合板中飞线组织和性能的影响

对钢—钢爆炸复合板进行退火试验,发现其中的飞线（ 绝热剪切线） 组织在一定的工艺下退火后会自行消失,但由其发展成的裂纹不会消失,经过论证指出：这种飞线是一种塑性变形线和裂纹源,同时它是在爆炸载荷下金属中出现的一种特殊的塑性变形机制。     

Influence of environment on fatigue crack growth in the threshold region

Low fatigue crack growth rates (down to 4 × 10⁻¹⁴m/cycle) were produced using a high frequency 20 kHz ultrasonic fatigue testing machine. The influence of non corrosive (silicone oil) and corrosive (3.5% sodium chloride solution) environments was compared. Down to crack propagation rates of some 10⁻¹⁰ m/cycle which corresponds to a crack growth rate of one lattice space per cycle no difference of crack growth rates was found. However, below this rate there seems to exist for non corrosive environments a threshold cyclic stress intensity, below which crack growth becomes diminishingly small, whereas no threshold was found for the corrosive environment. In the first case crack propagation is controlled by plastic deformation processes, in the second case these processes are markedly restricted. For this region, a transition in fracture mode from ductile transcrystalline to intergranular cracking was found.     

HRB355热轧带肋钢筋拉伸试样头部开裂分析

采用化学分析、金相检验和对比试验等方法,对HRB335 Ф36拉伸试样出现头部开裂的原因进行了分析。结果表明：试验使用平钳口,且未全部夹持是导致大规格拉伸试样头部发生开裂的主要原因。     

Enhanced stress corrosion resistance from steels having a dual-phase austenite-martensite microstructure

A high strength steel with an austenite-martensite duplex microstructure has been produced by extruding nickel coated steel powder. The austenite is stable and is present as a continuous network surrounding a high strength martensite. The dual-phase steel exhibits superior resistance to stress corrosion cracking in 3.5 pct NaCl solution, compared with steels of similar strength having conventional microstructures. Also, the effectiveness of the austenite in improving stress corrosion cracking resistance increases as the yield strength increases. The austenite, because of its inherent toughness, reduces the effective stress intensity at the advancing crack tip, and at the same time shields the crack tip from the corrosive environment.